For people with mood disorders such as bipolar disorder or major depressive disorder─complex, heterogeneous illnesses on their own─having other brain and behavior disorders at the same time is the rule rather than the exception. This concurrence of conditions, called co-morbidity, not only exacerbates symptoms, but also can greatly complicate treatment, making medications less effective or inappropriate. Treating these patients is currently a trial-and-error process.

Anxiety disorders, including panic disorder, obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD) and what is termed generalized anxiety disorder (GAD), which is an unrelenting state of exaggerated worry and stress, are the most common forms of co-morbidity with mood disorders. Studies have shown that over 85 percent of patients with bipolar disorder have some kind of anxiety problem. About 70 percent of bipolar patients showed some sort of impulse control disorder, such as attention deficit disorder (ADD) or attention deficit hyperactivity disorder (ADHD). For patients with major depressive disorder, or unipolar depression, the figure for co-morbidity with anxiety disorders is around 60 percent.

Another common co-morbidity problem is drug or alcohol abuse. A study conducted by Dr. Gao and his colleagues showed that around a third of the bipolar disorder patients they screened had substance abuse problems as well.

The immediate challenge researchers face in trying to understand and develop treatments for patients with multiple disorders is how to overcome the research complexities in trying to test what works for different patients with such vastly differing circumstances. And there is also the challenge of identifying and understanding the underlying biology.

To begin to address the immediate challenge─to meet the need for effective, validated treatment─Dr. Gao has initiated a study to test the efficacy of the anitpsychotic drug quetiapine (Seroquel) for the treatment of patients with bipolar disorder and co-existing general anxiety disorder and/or substance abuse. He and his group are also planning a comparable study with patients with unipolar depression and anxiety disorders. To implement the studies, they are systematically recruiting and diagnosing several hundred patients. The next step, further down the line, to understand how treatments work, will be to apply the information derived from the clinical studies to genetic studies of co-morbidity.